The present invention relates to improvements in apparatus for loading (and unloading) a hollow drum onto (and from) a cantilever-mounted axle adapted to support the drum for rotation. The apparatus of the invention is particularly useful for loading and unloading an image-recording or image-transfer drum in an electrostatographic printer/copier in which minimal clearance is provided between the drum surface and the various processing stations associated with the electrostatographic imaging process.
Referring to FIGS. 1-3, the above-referenced U.S. application Ser. No. 09/574,425 discloses an electrostatographic document printer 10 that comprises a pair of confronting, cantilever-mounted drums 12 and 16. Drum 12 typically comprises a hollow metal cylinder having a photoconductive outer layer 14 and serves to record images, in a conventional manner, via the well-known electrostatographic process. Briefly, as drum 12 rotates counter-clockwise, layer 14 is uniformly charged at a primary charging station 20, imagewise exposed with actinic radiation at an exposure station 22 to produce a charge image on layer 14, and subjected to toner particles that selectively adhere to the charge image to render such image visible. Continued rotation of drum 12 results in the intermediate transfer of the previously formed toner image to a non-stick outer surface 18 of drum 16. Thereafter, the image-recording surface of drum 12 is cleansed at cleaning stations 25 and 26, readying the drum for subsequent image recording. Meanwhile, the toner image on drum 14 is transferred to an image-receiver sheet (not shown), and the drum surface 18 is cleaned at a cleaning station 28. As will be appreciated, all of the aforementioned processing stations are precisely positioned in close proximity to the outer surfaces of the drums 12 and 16, and great care must be taken in removing the drums for servicing lest the drum surfaces be damaged by the hardware of the processing stations.
In the printer described above, drums 12 and 16 are rotatably supported by a pair of axles A2 and A3, respectively, that extend outwardly, in a cantilever fashion, from the rear mech plate RP of the printer support frame. Referring to FIG. 2, a solenoid-operated drum-support mechanism 32 serves to provide support for the free ends of axles A2 and A3 during drum rotation. Such support mechanism is movably mounted on a pivot mount 50 for movement between an operable position in which it supports both drum axles A1 and A3, and a stand-by position (shown in FIG. 2) in which it is sufficiently spaced from the drums to enable axial movement of the drums for removal and servicing. In use, the image-recording drum 12 is supported at its opposite ends 12A and 12B by a pair of gudgeons 40 and 42 that are releasably press fit into the respective ends of the drum. The rear gudgeon 40 is rotatably mounted directly on axle A2, whereas the front gudgeon 42 is rotatably mounted on a stub axle assembly A1 that, in use, is releasably connected to the free end of axle A2. When so connected, beveled edges on each gudgeon cooperate with beveled edges at each drum end to center the drum on the longitudinal axis of axle A2. As disclosed in the aforementioned application, when axle assembly A1 is disconnected from axle A2, drum 12 will slide off its supporting gudgeons and will be free to move axially, through an opening in the printer""s front mech plate FP for servicing.
As best shown in FIG. 3, careful axial movement of drum 12 from the printer frame is facilitated by a drum-loading/unloading structure 100 that is supported by axle A2 within the drum interior. The drum loading/unloading structure comprises a pair of discs 102, 103 and a plurality of interconnecting rods 104. Discs 102, 103 are provided with concentrically arranged central apertures 102A, 103A, each being adapted to receive and slide upon axle A2. Rods 104 are mutually parallel with each other and with the longitudinal axis of axle A2. The most radially outward surface of each rod extends slightly outside the perimeter of each of the supporting discs and lies on a circle having a diameter slightly less than the inside diameter of drum 12. The respective lengths of the rods, including their extensions 104A that extend beyond disc 103, are slightly less than the length of drum 12. Thus, upon removing gudgeon 42 from the end 12B of the drum 12, it will be appreciated that the drum will slide off the beveled edge of gudgeon 40 and thereby be collectively supported by several of the underlying rods 104 of the drum-loading/unloading structure. To remove the drum from axle A2, the operator grasps handles 106 mounted on disc 103 and exerts an axially outward force.
While the drum-loading/unloading apparatus described above is useful in reducing any damage to the drum surface as the drum is removed from the printer frame, it is problematic in certain respects. For example, it will be appreciated that axial movement of the drum will be supported by axle A2 only so long as the central aperture 103A of disc 103 maintains contact with the axle A2. Once contact is lost as the drum continues to move axially outward, it is up to the operator to assure that the drum axis remains substantially co-linear with the axis of axle A2; otherwise, the relatively delicate outer surface of the drum may physically contact the hardware of the various processing stations of the printer and cause damage. Ideally, the drum should be mechanically supported until the drum clears all potentially harmful surfaces as it moves axially from the printer frame. A further problem associated with the drum loading/unloading apparatus of the type described is that, being incapable of providing support for the drum at all times during of its axial movement, relatively slight defects in the drum surface cannot be addressed without totally removing the drum from the printer frame.
In view of the foregoing discussion, an object of the present invention is to provide an improved drum-loading/unloading apparatus of the type described, one that is substantially more robust than the prior art apparatus, and one that overcomes the aforementioned problems of the prior art apparatus.
According to the invention, an improved apparatus is provided for facilitating the loading and unloading of a hollow cylindrical drum, for example, an image-recording drum in an electrostatographic printer or the like, onto a drum axle having a free end extending outwardly in a cantilever manner from a support frame and having a longitudinally-extending axis about which the drum is adapted to rotate. According to a preferred embodiment, the apparatus of the invention comprises a plurality of telescoping slider mechanisms disposed at equal distances from each other and from the axis of the drum axle. Each of the slider mechanisms comprises a pair of elongated slide members extending substantially parallel to the drum axle. One of the slide members of each pair is rigidly supported by the drum axle, and the other slide member of each pair is slidably mounted on the rigidly supported slide member for movement parallel to the drum axle axis. The slidably mounted slide members of each pair cooperate to support the drum from within for axial movement between a drum-loading position axially spaced from the drum axle, and a loaded position atop the drum axle. Preferably, a total of three slider mechanisms are used to slidably support the drum, and each the slide mechanisms comprises a common drawer slider mechanism of the type commonly used to support a drawer in a cabinet for movement between a closed and open position. Preferably, a latching mechanism is provided to selectively latch the slidably mounted slide members in their respective drum-loading positions to facilitate loading of a drum onto the slide members.
The drum-loading/unloading apparatus of the invention is substantially more robust in construction than the aforementioned prior art structure, and it provides full support for the drum during axial movement of the drum between its operating position and a service position substantially spaced from the drum""s operating position, such as outside the support frame of the drum-utilization device. Thus, the drum may be handled and worked on, e.g., for cleaning purposes, without physically removing the drum from the loading/unloading apparatus. Further, the loading aid is significantly less costly to assemble and install in the supporting instrument.